What’s New in the 18th Edition

The following is a list of the more significant changes, clarifications, updates, and additions to The Chicago Manual of Style for the 18th edition. Items in the list are keyed to paragraph numbers in the 18th edition.

Part I: Publishing and Editing

Chapter 1: Books and Journals

Changed

1.47, 1.65. Chicago now prefers placing acknowledgments in the back matter rather than in the front matter for most types of books (CMOS itself is an exception).

Clarified

1.79. Book publishers are encouraged to list translators on the front cover (in addition to the title page).

New or expanded

1.17. New guidance on praise pages for books.
1.35. New guidance on disclaimers and other content notices on the copyright pages of books.
1.41. Expanded information on the placement of epigraphs and dedications in books.
1.43. New guidance on tables of contents for ebooks and audiobooks.
1.51. New guidance on adding accessible book cover descriptions.
1.64. Expanded information on ornamental or typographic section breaks, including the use of context breaks in HTML.
1.84, 1.101. Updated and expanded information on metadata for books and journal articles.

Chapter 2: Manuscript Preparation, Manuscript Editing, and Proofreading

Changed

2.86. Chicago no longer recommends using generic angle-bracketed labels as a markup strategy at the copyediting stage, though they may still be used for figure placement callouts and the like.

Clarified

2.65. Subheads can be styled in either title case or sentence case as long as treatment at each level is consistent.

New or expanded

2.3. New steps in the manuscript-to-book process outline specifically for self-publishers.
2.9. New guidance for authors on choosing fonts for their manuscripts.
2.12. Expanded guidance for authors on paper size and margins for their manuscripts.
2.20. New guidance for authors on creating tables of contents in their manuscripts.
2.54. New guidance on authenticity and sensitivity readings.
2.143. New guidance on checking for accessibility in electronic formats.
2.144. New guidance on preparing notes for an audiobook.

Chapter 3: Illustrations and Tables

New or expanded

3.28. New guidance on writing alt text for images.
3.29. New guidance on ensuring accessibility for math.
3.38. New guidance on citing AI-generated images.

Chapter 4: Rights, Permissions, and Copyright Administration

New or expanded

4.5. New information on AI (artificial intelligence) and copyright.
4.19. New information on rights retained by non-US licensors in copublications with US publishers.
4.28. Updated and expanded information on copyright duration for works published before 1978.
4.43. New coverage of copyright notices on unpublished manuscripts.
4.44. Updated and expanded coverage of authors’ names in copyright notices.
4.49. Revised and expanded coverage of deposit requirements with the US Library of Congress.
4.51, 4.76. New information on the responsibility of authors to specify whether and to what extent AI has been used in their work.
4.53. New coverage of copyright registration for successive editions of a work.
4.54. New information on making corrections or additions to a copyright registration.
4.65, 4.66, 4.67, 4.68. Updated and expanded coverage of open-access publishing models.
4.71. Updated information on authors’ use of their own works.
4.72, 4.73, 4.74. Updated and expanded coverage of Creative Commons licenses.
4.91. Updated coverage of fair-use considerations for epigraphs and song lyrics.
4.99. Updated and expanded coverage on the process of obtaining permission to use the work of others.
4.104. New information on accessible text descriptions offered by museums and other licensors.
4.112. Revised and expanded coverage of subsidiary rights categories.
4.115. New coverage of permissions considered as a separate category of licensing.

Part II: Style and Usage

Chapter 5: Grammar and Usage

Changed

5.51, 5.266. Chicago now endorses generic singular “they” as an option for referring to a person whose gender is unknown or unspecified or concealed for reasons of privacy.
5.254. The adverb “overly” is now accepted as unobjectionable.

New or expanded

5.3. New discussion of prescriptive versus descriptive grammar.
5.25. New coverage of distributive possessives.
5.34, 5.44, 5.45, 5.46. New coverage of grammatically singular uses of “they.”
5.79. Updated coverage on the use of articles with a series of coordinate nouns.
5.140. New coverage on mixing verb tenses in a single sentence or passage.
5.192. New coverage of verb agreement with “group of” and similar “of” phrases.
5.212. New guidance on when to omit “that.”
5.255–67. Revised, updated, and expanded coverage of inclusive language and strategies for minimizing bias, including new or expanded coverage of person-first versus identity-first language, ableism, and options for achieving gender neutrality (including the use of singular “they”).

Chapter 6: Punctuation

Changed

6.25. A comma is no longer required between imperative clauses joined by a coordinating conjunction.
6.67. The first letter of a complete sentence following a colon is now capitalized.
6.85. An en dash rather than a hyphen should be used between the names of two or more people used as a compound modifier before a noun (e.g., “Ali–Frazier match”; “Epstein–Barr virus”).

Clarified

6.24. It can be acceptable in some cases to add a comma before a coordinating conjunction that joins a compound predicate.
6.43. No comma is required before a quotation introduced with a dialogue verb plus a linking verb.
6.120. A trailing slash at the end of a URL can usually be retained.
6.129. A narrow no-break space (U+202F) may be used in electronic formats wherever a nonbreaking thin space would be used in print.
6.134. If needed for sense, a comma may follow a question mark or exclamation point at the end of quoted text not presented as dialogue.
6.141. Each item in a list that consists of a mix of complete sentences and fragments should end in a period (though revising the list to make it consistent is usually the better option).

New or expanded

6.23. New guidance on run-on sentences and comma splices.
6.31. Expanded guidance on spousal and other relationship commas.
6.119. New guidance on using slashes as delimiters in pronunciations.
6.136. New guidance on punctuating questions that introduce lists.
6.137. New guidance on using punctuation relative to emojis.

Chapter 7: Spelling, Distinctive Treatment of Words, and Compounds

Changed

7.56. German nouns used in an English-language context are now capitalized if listed as such in Merriam-Webster.
7.68. An apostrophe is now used before the “s” to form the plural of a capital letter.
7.82. Chicago now prefers “space bar” (not “Space bar”), following Merriam-Webster.
7.96 (sec. 3, under “e”). The word ebook is now closed rather than hyphenated, and esports has been added (as one word).
7.96 (sec. 3, under “elect”). The term “elect” should be joined to an open compound with an en dash rather than a space (e.g., “vice president–elect”).
7.96 (sec. 3, under “half”). Adjective compounds with “half” are open rather than hyphenated after a noun (e.g., “it was half finished”).
7.96 (sec. 3, under “mid”). The word “mid” is now treated as an adjective combining form rather than as a prefix; compounds with “mid” are therefore hyphenated unless listed as closed in Merriam-Webster.
7.96 (sec. 3, under “then”). Terms modified by the adjective “then” are now hyphenated (e.g., “then-president”) or, before an open compound, joined to “then” by an en dash (“then–vice president”).

Clarified

7.11. Subject to editorial discretion, certain names ending in a pronounced “s” can remain in singular form when used as a plural (e.g., “three Mercedes”).
7.47. If needed, an end-of-line break may be made before a colon in a URL (except for the colon in “http:” or “https:”).
7.66. Proper nouns used as words are italicized (e.g., “the word Celsius”), whereas names used as names are not (“the name Celsius”).
7.85. The formal names of internet protocols are capitalized but may be lowercased when referred to generically.
7.91. An open compound noun listed as such in Merriam-Webster may remain unhyphenated as a compound modifier before another noun unless ambiguity threatens (e.g., “high school” in “high school students”).
7.92. Certain compound modifiers are always hyphenated, even after the noun they modify.
7.93. Words ending in -ly that are adjectives rather than adverbs are hyphenated before the noun as part of a compound adjective (e.g., “early-morning walk”).
7.95. A suspended hyphen may be used when the first part of a hyphenated compound is omitted (e.g., “state-owned and -operated hospitals”).

New or expanded

7.53. New guidance on using asterisks for emphasis.
7.59. New guidance on choosing terms for hyperlinked text.
7.74. New guidance on styling communication code words (includes the NATO phonetic alphabet).
7.86. New guidance on styling hashtags in social media and other contexts.
7.96 (sec. 2). New guidance on hyphenating adverbial phrases.
7.96 (sec. 3). New guidance on hyphenating compounds formed with “first,” “second,” and “third.”

Chapter 8: Names, Terms, and Titles of Works

Changed

8.22. Personal titles used before a name are now capitalized even when modified by an adjective (e.g., “former President Carter”).
8.39. The adjective “Indigenous” is now capitalized when referring to people. “Black” is also usually capitalized, and “White” may be capitalized if a particular author or publisher prefers.
8.48. The terms “Midwestern” and “Midwesterner” are now capitalized, as are analogous terms related to a region of the United States or similar entity.
8.48. The term “equatorial current” is now lowercased, but specific equatorial currents are capitalized (e.g., “South Equatorial Current”).
8.48. The word “continent” in “Antarctic continent” is now lowercased.
8.52. The word “County” is now capitalized in the names of Irish counties.
8.54. The word “River” is now capitalized in “the River Thames.”
8.54. The word “valley” is now capitalized in “Nile River Valley,” “Nile Valley,” and “Mississippi River Valley,” and “delta” is now capitalized in “Nile Delta.”
8.58. The Colossus of Rhodes is now referred to in shortened form as “the Colossus” (with a capital “C”).
8.62. Adjectives derived from proper nouns are now capitalized if capitalized as a first-listed entry in Merriam-Webster, even if the use is not strictly literal (e.g., “Swiss cheese”).
8.68. The terms “far right” and “far left” are now lowercased, as are “radical right” and “radical left.”
8.71. The word “Talk” is now capitalized in “TED Talk.”
8.81. The word “Agreement” is now capitalized in “the Munich Agreement.”
8.90. “Day” is now capitalized in “D-Day.”
8.91. The names of time zones now capitalized (e.g., “Central Daylight Time”; but “Central time”).
8.136. Words like “Eon” and “Era” are now capitalized when they follow a formal geographic name (e.g., “the Archaean Eon”).
8.139. The word “comet” is now capitalized as part of a named comet (e.g., “Halley’s Comet”).
8.149. When referring to the origins of the universe, the term “Big Bang” is now capitalized to avoid confusion with the generic sense of those words.
8.159, 8.160. “Headline style” and “sentence style” are now referred to as “title case” and “sentence case,” respectively.
8.160. Prepositions of five letters or more are now capitalized in the title of a work (e.g., A Room with a View but Much Ado About Nothing).
8.162. Subsequent elements in a hyphenated term that begins with a prefix are now capitalized in a title according to the general rule for title capitalization (e.g., “Anti-Intellectual Pursuits”).
8.172. An initial The is now capitalized in running text when it forms part of the official name of a periodical (e.g., The New York Times) but may be omitted in source citations.
8.175. Terms that would be italicized in running text remain italic in an italicized title of a book or other work rather than being set in ordinary text (or “reverse italics”); however, the title of a book or other work within another title is still placed in quotation marks.
8.193. The name of a website is now usually italicized if it belongs to one of the categories that would normally be italicized (e.g., book or periodical); this applies whether or not there is (or was) a printed counterpart.
8.197, 8.198. The abbreviation “No.” is now capitalized within the title of a musical work except when following an opus number.

Clarified

8.52. The governmental entity is “State of Washington,” not “Washington State” (the latter of which should be styled as “Washington state” in most contexts).
8.92. Referred to generically, the word “god” is usually lowercased (e.g., “a god,” “gods”).
8.92. Some writers will prefer lowercase “god” in expressions that could otherwise be considered profane.
8.113. Words like “army” and “navy” are usually capitalized in works primarily about the US military, even when standing alone (e.g., “the Army”).
8.167. A hyphen next to an open compound in the title of a work may be changed to an en dash, and quotation marks may be adjusted to conform to the style of the surrounding text.
8.178. Series titles based on a title in the series can usually be italicized (e.g., “the Twilight series”), but roman may still be used for names based on a place or character in the work (“the Ramona series”).
8.193. Generic web page titles like Help or About are capitalized but not placed in quotation marks.
8.194. Titles of news websites can usually be treated like the titles of other periodicals and italicized.

New or expanded

8.6. New guidance on styling screen names and other aliases.
8.165. New guidance on styling titles of works when italics are not an option.
8.203. New guidance on styling the names of memes.

Chapter 9: Numbers

Changed

9.5. A year expressed as a numeral can now begin a sentence, though it is preferable to preface it with “The year.”
9.5. Terms that consist of a combination of numerals and words (e.g., “7-Eleven”) can now begin a sentence.
9.33. Numerals rather than words can now be used for days of the week expressed as ordinals, even when used alone (e.g., “the 25th of May,” “the 25th”).

Clarified

9.7. Numerals rather than words may be used for certain categories of numbers (e.g., ages, centuries, and numbered editions) if many of these appear in a work.
9.14. Numerals may be used for an exact quantity that might otherwise be spelled out.
9.20. “Less” rather than “fewer” may be used with percentages, even when referring to nouns that would otherwise be countable.
9.39. Though numerals are normally preferred with “a.m.” and “p.m.,” words may be used if done so consistently, as in fictional dialogue (e.g., “two a.m.”).

New or expanded

9.8. New guidance on when numerals are always used, including a list of examples by category.
9.25. Bitcoin symbol added to currency examples.

Chapter 10: Abbreviations

Clarified

10.3. Subject to editorial discretion, an abbreviation may be spelled out the first time it appears in each new chapter or other major division of a work.
10.17. The abbreviation “CDR” (military usage) usually becomes “Cmdr.” (not “Cdr.”) in common usage.
10.55. Though the abbreviation DOI is a trademark, the spelled-out form “digital object identifier” may be lowercased.
10.64. In the context of firearms, the space between a numeral and an abbreviated unit of measure may be omitted in expressions of caliber and the like used as a modifier before a noun (e.g., “a 9mm Luger”).
10.76. “Week” may be abbreviated as “wk.” (with a period).

New or expanded

10.11. New guidance on abbreviations at the beginning of a sentence.
10.25. New guidance on abbreviations related to race and ethnicity.
10.26. New guidance on abbreviations related to gender identity and sexual orientation.
10.27. New guidance on abbreviations related to health and disability status.
10.78. New guidance on styling social abbreviations and emojis.

Chapter 11: Languages Other than English

Changed

11.4. Words from other languages used as part of the vocabulary of a multilingual author, narrator, or character no longer need to be italicized.
11.87. A hyphenated “al-” at the beginning of a proper noun transliterated from Arabic may remain lowercase at the beginning of the title of a work.

Clarified

11.16, 11.17. Machine translations should be credited with the name of the machine translation service but may be edited without the use of square brackets.
11.29. The names of French organizations and institutions can be capitalized in title case in an English context (e.g., “Bibliothèque Nationale”).
11.44. Single versions of German quotation marks may be used for quotations within quotations.

New or expanded

11.7. New guidance on using language tags in electronic formats.
11.48. New information on the capital form of the German sharp “s.”
11.49–52. New coverage of Indigenous languages.
11.95, 11.96. New coverage of Korean romanization.
11.119. New guidance on South Asian capitalization for transliterated text.

Chapter 12: Quotations and Dialogue

Note: Though chapter 12 in the 17th edition, “Mathematics in Type,” has been removed for the 18th edition (and the remaining chapters renumbered), basic mathematical concepts are still covered in the Manual. See the section on math near the end of this list for details.

Changed

12.43. A comma is no longer required between an ellipsis and a speech tag in quoted dialogue.

Clarified

12.35. When a source attribution introduced with an em dash is run in to the end of an epigraph instead of being presented on a new line, no space appears before the em dash.
12.44. In fictional dialogue, it is permissible to use more than two em dashes in a single sentence.

New or expanded

12.38. New guidance on editing and formatting publicity reviews and blurbs.
12.41. New guidance on using speaker tags in dialogue.
12.42. New guidance on punctuating interrupted speech.
12.44. New guidance on punctuating stuttering and the like.
12.45. Expanded guidance on styling dialogue that spans multiple paragraphs.
12.46. New guidance on punctuating quotations within quoted dialogue.
12.48. Expanded coverage of fictional dialogue formatted without quotation marks.
12.49. New guidance on using italics to set off thoughts and other internal discourse.
12.50. New guidance on formatting text messages and the like in fiction.
12.51. New guidance on the use of abbreviations in dialogue.
12.52. New guidance on the use of parentheses in dialogue.
12.57. New guidance on editing interviews transcribed by authors.
12.68. New guidance on the Unicode ellipsis character (…) and unspaced periods (...).

Part III: Source Citations and Indexes

Chapter 13: Source Citations: Overview

Changed

13.23, 13.107. Up to six authors are now listed in a bibliography or reference list entry; if more than six, only the first three are listed, followed by “et al.” In a shortened note or an author-date text citation, up to two authors are now listed; if more than two, only the first is listed, followed by “et al.”
13.26. A month or season can now usually be omitted in citations of journal articles.
13.72, 13.113. Chicago now prefers repeating the name of the author(s) rather than using a 3-em dash to stand in for repeated names in bibliographies or reference lists.
13.94. Books with “and Other Stories” in the main title no longer require a comma before “and,” and the main title is now placed in quotation marks (e.g., “A River Runs Through It” and Other Stories).

Clarified

13.37. Shortened citations used instead of “ibid.” may take one of three forms: author-title (Chicago’s regular short form), author-only, or title-only.
13.47. Required elements of a citation that have been mentioned in the text can often be omitted from a footnote (because of its proximity to the text) but not usually from an endnote.
13.75. Authors whose names follow Eastern order (family name first) rather than Western order (family name last) are not normally inverted in a bibliography or reference list.
13.91. The subtitle “A Novel” can usually be omitted when the title of a book is mentioned or cited, even if it appears on the title page.
13.100. An initial “A,” “An,” or “The” in a title is ignored when alphabetizing successive works by the same author by title in a bibliography or reference list (but a “Le,” “Un,” or the like is not ignored).

New or expanded

13.5. New guidance on the difference between mentioning sources and citing them.
13.11. Expanded guidance on using shortened URLs in citations.

Chapter 14: Source Citations: Examples

Changed

14.8. The page range for a cited chapter in an edited book is no longer required in a bibliography or reference list entry (though a page range is still required for most journal articles).
14.30. A place of publication is no longer required in citations of books.
14.36. The phrase “published by the author” (abbreviated “pub. by author” in a note) is now preferred over “self-published” in citations of books published independently.
14.36. When citing a self-published book, it is no longer necessary to list a commercial distribution platform such as Amazon or Smashwords.
14.115. Information about a cited presentation is no longer enclosed in parentheses in a note.
14.133. Museum accession numbers should be included in citations of artworks when they are available.

Clarified

14.12. If the same person is cited as both author and editor of a work, the name is given in full for both roles.
14.34. If a publisher’s name appears on one source with “and” and another with “&,” it may be made consistent throughout a bibliography or reference list (and anywhere else the name appears).
14.40. A distributor’s name should be included in a bibliography or reference list entry for a book if it is listed on the title page.
14.56. A note that spans two pages would be cited as, for example, “10–11n5” (for a note number 5 that spans pages 10 and 11).
14.56. When citing a note on a page numbered with Roman numerals, a space should be used between the page number and the abbreviation “n” (for “note”).
14.58. Books consulted in a fixed-page format that matches a printed counterpart can be cited without naming the format (as if it were print).
14.85. An abstract for a journal article may be mentioned in text or in a note, but a bibliography or reference list entry should cite the article as a whole.
14.89. Author-date reference list entries that include a month and day (as for a newspaper article) do not need to repeat the year with the month and day.
14.90. A period in the middle of a newspaper headline may be changed to a colon.
14.114. Unpublished manuscripts that are unavailable for others to consult may be mentioned in the text or in a note but are not usually included in a bibliography or reference list.
14.134. The abbreviation “exh. cat.” may be used for an exhibition catalog cited in a note.

New or expanded

14.6. New guidance on citing an illustrator in addition to an author.
14.75, 14.76. Updated and expanded guidance on citing ahead-of-print and forthcoming journal articles as well as preprints.
14.104. New guidance on citing sources archived via the Wayback Machine or similar service.
14.112. New guidance on citing AI-generated content.
14.136–37. New guidance on citing Indigenous sources.
14.157. Updated and expanded guidance on citing databases and datasets.

Chapter 15: Indexes

Changed

15.66. Chicago now prefers the word-by-word system of alphabetization over the letter-by-letter system (but will accept either in a well-prepared index).

Clarified

15.16. “See” references in an index should not include locators.
15.20. “See also” references should not lead to an entry that does not list any page numbers not included in the original entry.
15.59. If a subtitle is included in the indexed title of a work (it is normally dropped), an initial article in the main title is inverted by placing it after the main title (preceded by a comma) but before the subtitle.
15.85. When the same family name is inverted for one person but not for another (e.g., “Li Jinghan” and “Li, Lillian”), the names may be listed together and alphabetized by first names regardless of the comma.
15.98. If the newer form of a term is indexed but the older form is also mentioned in the text, the older term may be mentioned in the index entry (in parentheses).
15.98. Names like Mauna Loa are not usually inverted in an index, but if they are inverted, a headnote should explain this choice.
15.138. In long or complex indexes, it is acceptable to add “continued” lines for every index entry that breaks at the end of a column rather than only for those that break across a recto to a verso page.

Math (formerly chapter 12)

In lieu of a separate chapter on math, the 18th edition features information designed to help general editors, some of it adapted from chapter 12 in the 17th edition.

3.29. Accessibility for math presented online.
6.108. The order of delimiters (including parentheses and brackets) in mathematical expressions.
6.130. Spaces in mathematical expressions.
7.45. Dividing mathematical expressions at the end of a line.
7.73. Style for mathematical variables.
9.17. Fractions in mathematical contexts.
10.70. Common mathematical signs and symbols.
10.71. Beginning a sentence with a mathematical symbol.
12.69. Ellipses in mathematical expressions.

Glossary

More than fifty new terms, most of them related to editing.

Bibliography of Additional Resources

New sections on inclusive language and accessibility.